Solar Panel solely for charging batteries off grid.

[SLC]

Management has decreed that our 60’ narrowboat needs solar panels, primarily to charge the batteries when we are out and about so that we can leave the boat for a few days and not worry about the batteries discharging or having to run the engine every so often for a few hours, the latter being a waste of diesel, bad for the environment and possibly disturbing fellow canal users.

Unfortunately, our lovely boat is an example of style over practicality as we have 3 large pigeon boxes and 4 mushroom vents along the centre line of the boat. This makes permanently fixing a small solar panel difficult especially if we want to keep the headroom low. There is of course also a centre line hook and rope to fit in without snagging on the panels.

So, one solution management prefers is perhaps a 200W portable panel which comes in a suitcase for easy storage and folds out.  Designed really for motor homes, cars and camping, it comes with controller and cable and (uncertain) connectors with what looks like car battery clips on the end for connecting to the battery! Theory is that you moor up, get the panel out from behind the bed, place it on the roof securing it with something, connect the battery, lock the boat up for a few days and keep the batteries charged up! Management thinks that is easy!

 

Instinctively, I do not like this:
1.    The panel could be stolen. Furthermore, depending upon how the cable is connected, damage could be done to the installation when the cable is pulled out by the thieves.
2.    When mooring and setting up the panel I would want to ensure that the batteries are connected first before the panel is connected. i.e include a switch somewhere before the controller.
3.    Assuming I can find a gap to run the cable (of the right gauge), how do I connect the cable to the batteries ensuring that a suitable fuse is placed as close to the batteries as possible. This suggests fixed wiring run from the batteries, through the controller, an isolating switch and then out through a roof gland to a suitable connector. What type of fuse and indeed  what type of switch?
4.    The aforementioned connector needs to be waterproof so that when the panel is not in use water and damp does not get in. The panel does not appear to have a MC4 connector so I will need to terminate cables in the appropriate way using a special tool.

My preference is for a permanently fixed 200W solar panel (IF possible) with proper MC4 connectors on the roof going through a roof gland leading to a fused switch to isolate the panels if necessary. Then permanent wiring to and from the controller can be added with the batteries connected via a fuse as close as possible to the batteries.
Comments as to how best we can and should do this bearing in mind safety of operation is paramount? Also, what other problems may I encounter or have overlooked?
 

[Arthur Marshall]

When I were a lad, before all this major solar stuff took off, you could get a small panel that sat in a window and plugged into one of the 12v power sockets and trickle charged the battery. Pretty inefficient, but I got the impression it did actually work. I'm sure someone will know more...

[smiler]

Can you not mount the panels on brackets just above the mushroom vents?

[Tony Brooks]

29 minutes ago, Arthur Marshall said:

When I were a lad, before all this major solar stuff took off, you could get a small panel that sat in a window and plugged into one of the 12v power sockets and trickle charged the battery. Pretty inefficient, but I got the impression it did actually work. I'm sure someone will know more...

 

Maybe they would keep up with the self discharge on a car battery, possibly with a little bit extra. I can't see it ding much actual charging on a boat battery bank.

Edited May 1 by Tony Brooks

[BEngo]

I have one of the panels Arthur remembers.  It keeps up with the self-discharge and quiescent loads of a car.  Just about, provided the sun shines enough.

 

If mounting the panels permanently is really not feasible I would put a gland box on the roof with two opposite polarity MC4 connectors, or an Andersen connector, then permanently wire a connection set up intermally that goes DP switch, controller, fuse  batteries.  Connect the panel(s) to suitable length cable  tails terminated to match the connector near the gland box.

You will need suitable mechanical securing arrangements  for the portable panel(s), lest they get airborne in the first gale.

 

N

[robtheplod]

I'd fit something rather than have a folding option - will soon get tiring having to get that out...... surely there must be some room for a small panel?

[Jen-in-Wellies]

19 minutes ago, robtheplod said:

I'd fit something rather than have a folding option - will soon get tiring having to get that out...... surely there must be some room for a small panel?

Or several small panels, wired either in series, or parallel in the gaps between the roof furniture. Unfortunately, the cheapest panels these days per Watt are the largest, as they are massed produced for buildings and solar farms. Several small panels will be more expensive for the same output.

If the OP does go for a removable panel, then I'd look at something other than MC4 connectors for plugging it in. They aren't designed for frequent connection and disconnection. Possibly something like Anderson connectors.

 

[David Mack]

How big is the biggest space between pigeon boxes/mushroom vents?

How much space could you create if you replaced on of the mushroom vents with a low profile flying saucer vent and mounted the panel above it?

[JoeC]

A picture of the top of the boat would help us to help you.

[MtB]

Also mushrooms, albeit not easily, can be moved to make space. 

 

So can pigeon boxes, though even less easily. 

 

 

 

(Although David's suggestion of converting obstructing mushrooms into flying saucer vents and just putting the panels over them is a very good idea. Better than moving them.)

 

 

[Hudds Lad]

15 hours ago, Arthur Marshall said:

When I were a lad, before all this major solar stuff took off, you could get a small panel that sat in a window and plugged into one of the 12v power sockets and trickle charged the battery. Pretty inefficient, but I got the impression it did actually work. I'm sure someone will know more...

I've seen a few cars on private moorings with small ones in the windscreen, about £30 on Amazon for example.

[Tony Brooks]

1 hour ago, Hudds Lad said:

I've seen a few cars on private moorings with small ones in the windscreen, about £30 on Amazon for example.

 

Yes, that is what they are designed for - say about a 35Ah start battery only, whereas a boat has typically 3, 4 or more 110Ah domestic batteries connected in parallel, so each battery's self discharge is multiplied by the number in the bank.

 

Personally, I am doubtful if, with the way boats see to be used today, 200 watts of solar would allow several days tied up without engine running, but that depends on the boater's electrical needs.

[SLC]

I need to visit the boat to measure up and the pictures I have are not ideal. Therefore I was going to wait until I do but here are some. Since taken, we have added a Fairlead adjacent to the centre line hook. This is one from the front of the boat and shows the 5 mushroom vents and 3 pigeon boxes.

This one is looking towards the front of the boat where a panel could go but for the centre line rope could get caught.

[Peanut]

I see the boat is in a marina, but when you are out and about, the batteries will be charged by the engine. At the end of the day, you moore up, and soon the sun goes down. I think the plan would wast the best of the favourable sun, and not produce as much as it might if the panels were out all day.

[robtheplod]

4 hours ago, SLC said:

I need to visit the boat to measure up and the pictures I have are not ideal. Therefore I was going to wait until I do but here are some. Since taken, we have added a Fairlead adjacent to the centre line hook. This is one from the front of the boat and shows the 5 mushroom vents and 3 pigeon boxes.

This one is looking towards the front of the boat where a panel could go but for the centre line rope could get caught.

loads of room!    

[blackrose]

On 01/05/2024 at 19:54, smiler said:

Can you not mount the panels on brackets just above the mushroom vents?

 

I see people doing this but what's the point of the mushroom vent if there's a big panel above it?

 

Better to remove the mushroom vent entirely and put a thick bead of PU sealant on the roof around the perimeter of the hole to stop any wind blown water getting in. Mount the solar panel above the hole as low as you can, obviously making sure there's a gap.

 

That's what I've done and it works perfectly. There's still a vent and the panels sit lower, so I haven't increased the air-draught and it still looks ok.

 

The height of the frame around the panel ensures that the underside of the panel is about an inch above the hole.

 

Edited May 2 by blackrose

[Iain_S]

We currently have a portable panel on Kelpie. It’s a bit of a faff, to be honest. One has to be really careful putting it on the roof, lest one scratch the paint, so I have a tarpaulin with magnets on it which gets put on the roof first for protection. I do find that I’m constantly adjusting the thing to achieve maximum ( but fairly low!) output.

 

Plans are afoot to improve things a bit, but the other half is not keen on the roof getting cluttered up with panels, so current thinking is semi flexible stick on CIGS panels. I also need to get a round tuit …

[blackrose]

5 hours ago, SLC said:

This one is looking towards the front of the boat where a panel could go but for the centre line rope could get caught.

 

If you have 2 centre ropes going through a fairlead on the handrail on each side then the ropes shouldn't interfere with your panels. But you must make sure the fairleads are solidly mounted. A couple of brass screws really won't do unless you don't mind a snapped off fairlead hitting you in the face!

[MrFish]

You could go for semi flexible panels going length ways down each side of the vents. 

[blackrose]

3 minutes ago, MrFish said:

You could go for semi flexible panels going length ways down each side of the vents. 

 

Do you mean stick on panels? 

 

The main problem with them is that they get too hot and lose efficiency. If you don't have much space for big panels you want them to be as efficient as possible.

Edited May 2 by blackrose

[Jen-in-Wellies]

19 minutes ago, blackrose said:

 

If you have 2 centre ropes going through a fairlead on the handrail on each side then the ropes shouldn't interfere with your panels. But you must make sure the fairleads are solidly mounted. A couple of brass screws really won't do unless you don't mind a snapped off fairlead hitting you in the face!

After losing the first fairlead from this, I replaced all the brass bolts with stainless steel and increased the size from M4 to M6.

Can confirm that two centre rope, plus handrail fairleads play nicely with solar panels.

[Alan de Enfield]

1 hour ago, Iain_S said:

I also need to get a round tuit …

 

 

Here you are - no excuse now ... 

 

[jeanb]

3 hours ago, blackrose said:

 

The height of the frame around the panel ensures that the underside of the panel is about an inch above the hole.

 

I think that looks very neat.

[blackrose]

Thanks. I'm just trying to demonstrate that if you have a panel over a mushroom vent you don't need the brass vent anymore. I think perhaps some people are scared to remove them? Unless of course they want the central bracket in order to angle the panel. I can angle my panels too using a different system.

[Jen-in-Wellies]

9 hours ago, blackrose said:

Thanks. I'm just trying to demonstrate that if you have a panel over a mushroom vent you don't need the brass vent anymore. I think perhaps some people are scared to remove them? Unless of course they want the central bracket in order to angle the panel. I can angle my panels too using a different system.

Possibly a left over from the days when not meeting ventilation area was a BSS fail for private boats, rather than an advisory, as it is now.